On the river-lake relationship of the middle Yangtze reaches

The geological and meteorological setting of the Jianghan-Dongting lake area leads to high precipitation and siltation, but poor water discharge, thus the area is frequently flooded. In the past the river-lake relationship of the Middle Yangtze has been variable but has deteriorated recently under increasing human influence. The Jianghan Plain of the Middle Yangtze becomes a waterlogged lowland under the constant threat of flooding from the perched Jingjiang River. Due to siltation and land reclamation the Dongting Lake has lost most of its regulatory function for the river and has become increasingly vulnerable to flood disasters. The Middle Yangtze River has been undergoing siltation, resulting from a downstream decline of sediment transport capacity, resulting in the elevation of the flood level above the lowlands. Heightening of the levees has caused further siltation of the channel. The Three Gorges Reservoir will provide a buffering period of 50-80 years, during which much of the silt will be trapped in the reservoir and scouring downstream may occur. We should utilize this period to work out an overall resolution to the problem. Construction of a water and silt diversion project in the Honghu Lake and surrounding areas may resolve this problem in the dangerous Chenglingji-Wuhan Segment of the Yangtze. Widening the canals connecting the Middle Yangtze and Han Rivers may function as a discharge-dividing channel of the Yangtze, which may prove to be beneficial. (c) 2006 Elsevier B.V All rights reserved.